Just how accurate are Alexa, Compete, Quantcast & the others?

Today we’re going to examine a number of tools and resources for getting insights into competitors’ traffic data. We’ll assess their strengths and weaknesses as well as the validity and usefulness of the data provided.

We’ve had clients asking us for a better view of overall market size and what kind of traffic their competitors are getting, since it can be tricky to find meaningful predictive data even when you know who your competitors are or should be.

It is worth pointing out that a number of these services suggest they can provide better data if you claim the sites by entering your ownership credentials. I can’t testify to the accuracy of this, and our analysis is based upon the free version of the tools as we did not have paid access to any of the tools.

We tested 25 sites for which we had reliable internal data, giving us insight into just how accurate these tools really are — or aren’t.

Alexa: Too often, dubious numbers

1Strengths:Alexa is good for comparing different sites traffic and for monitoring general traffic trends. It can be quite useful for comparing one site to a competitor site (up to five sites at a time). The index is massive and contains some data about all of the 25 sites we tested.

Weaknesses: Not so great for the smaller sites. As you can see below, you won’t get any of the traffic charts for sites ranked outside of the top 100,000, which means if Alexa thinks you are getting fewer than 10,000 visits per month you’re unlikely to glean any great information. Accuracy is a serious concern. This does call into question the usefulness of the tool in general. The numbers reported are not helpful for predicting traffic on their own.

Accuracy: We want to keep this all anonymous but let’s just say one site that we know gets 10-20,000 visits per month had an Alexa rank that was more than five times better than a site that we know gets 75,000+ visitors per month. And this was not just a one-off event. So I have to seriously question the reliability of this tool. It didn’t seem to be too bad at predicting the trends for a single site but the charts are extremely difficult to make any real use of. Interestingly it seems to be skewed in favor of sites within the search marketing space. Sites in the search marketing space that we looked at regularly outranked sites receiving more than 10 times as much traffic on a monthly basis.

How to best use Alexa: The tool is interesting for comparing similar sites or sites within an industry, but be very cautious about using this to make any meaningful suggestions or estimates on traffic data. The most accurate data seemed to be the data from the visitors by country — the percentages we looked at were not too far off.

Cost: Free. Options for site audits for $199.

Compete: Good UI, questionable data

2Strengths:Compete has a useful interface, speaks the right language (unique visitors, visits, etc.), offers the ability to compare multiple sites, and its data is easy to understand and well presented.

Weaknesses: Accuracy, somewhat limited number of sites – many sites that it classifies as “low sample sites,” and the cost of the Pro option.

Accuracy: Again, accuracy is a serious concern here. The data was off in some cases by as much as 2,000% for monthly visits. The accuracy seemed to be a bit better for the peaks in traffic and some of the general trends we looked at but was certainly not reliable enough for us to suggest reporting competitor traffic based upon this information.

How to best use Compete: It should come as no surprise that Compete is best used for comparing competitors. The scale of the data is way off but some of the trends seemed to be fairly reliable. I wouldn’t advise reporting any numbers from this data as they do not seem close/reliable at all – often off by a factor of 200% or more — however the trends are reliable. The information could be meaningfully used to look into seasonal trends between competitors.